Assessment of Performance and Deactivation Resistance of Catalysts in the Pyrolysis of Polyethylene and Post-Consumer Polyolefin Waste

Abstract

In the present work, the catalyst performances of USY and REY zeolites and MgO, ZnO, and Mg_xAlO_y oxides are investigated in the pyrolysis of virgin high-density polyethylene (HDPE) and of post-consumer polyolefin waste. The influence of operation parameters and catalyst deactivation resistance over four reaction cycles are evaluated. The results indicate that basic oxides do not show relevant cracking activity, so that the only identified effect for these catalysts is the production of liquid products with higher contents of paraffins when compared to thermal pyrolysis. Among the evaluated oxides, Mg_xAlO_y is the most active and resistant to deactivation. The zeolites promote cracking and secondary reactions of isomerization, cyclization, and aromatization. Particularly, USY promotes the production of higher-quality oils and shows higher deactivation resistance, when compared to REY. Additionally, a significant loss of catalyst activity is identified in reactions conducted with post-consumer polyolefin wastes. However, increase in rates of coke formation and the presence of contaminants (such as halogens and metals) are not detected in the catalysts after the reactions.